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16' duct design
- Thread starter par060
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MiketheEngineer
Structural
What and how much, how fast are you wanting to ove it??
- Thread starter
- #3
It would be nice if I could find something online so I could read it for nothing and have it right away. Im looking to find the stresses and how to determine the allowables...... I could run it in SAP2000 but Im really interested in finding the typical checks that one would do
racookpe1978
Nuclear
What gasses?
(Hazardous? High temperature? Chemically reactive, or just "cold air"? Deadly (carbon monoxide or H2S or sulphates or chlorides or the like?)
What pressures?
What flow rates?
How long? How high off the ground?
For example, a gas turbine exhaust is about 15 foot in diameter, but 1200 degrees and is moving at very high speeds into a heat recovery steam generator or direct-to-air exhaust.
A "air conditioner" return is moving clean air at low speeds and almost no pressure.
A boiler suction inlet piping is leading to a blower, but has significant restrictions based on fan position, filter and room spaces, and fan/boiler relative movement.
You've told us nothing useful.
(Hazardous? High temperature? Chemically reactive, or just "cold air"? Deadly (carbon monoxide or H2S or sulphates or chlorides or the like?)
What pressures?
What flow rates?
How long? How high off the ground?
For example, a gas turbine exhaust is about 15 foot in diameter, but 1200 degrees and is moving at very high speeds into a heat recovery steam generator or direct-to-air exhaust.
A "air conditioner" return is moving clean air at low speeds and almost no pressure.
A boiler suction inlet piping is leading to a blower, but has significant restrictions based on fan position, filter and room spaces, and fan/boiler relative movement.
You've told us nothing useful.
- Thread starter
- #5
the duct is moving dust and air to a bag house. The internal pressure ...Im not sure its not that great....the internal temp is about 250 degrees. the total length might be hundreds of feet so it will have intermediate supports maybe every 20' or so.....the loads Im looking at are wind,siesmic......there will be some alowance for build up of dust inside....I think they just use a nominal internal pressure. COming up with the loads isn't an isssue really I think I'd just like to get some guidance on the allowables...
racookpe1978
Nuclear
D**m.
Dust and air moving to a baghouse at 250 degrees over several hundreds of feet?
You are talking serious danger of explosions! If not from an external spark, from internal (flow-related) static charges building up.
Dust and air moving to a baghouse at 250 degrees over several hundreds of feet?
You are talking serious danger of explosions! If not from an external spark, from internal (flow-related) static charges building up.
racookpe1978
Nuclear
Having said that, you will not, at least, suffer from internal pressure problems - other than leaks of the highly dangerous, explosive, high-temperature dust.
Structural loads on the 16 foot (5+ meter) diameter duct will include:
- Self-weight of the cylinder pieces - as they are fabricated, as they are shipped, as they are erected, and in-place (gravity) loads will distort and warp each section.
-External wind loads on each piece after erection.
-Warping from settlement of the assembly.
-Seismic?
Static, external loads: snow and ice loads?
-Vibration and internal loads as the weight of the dust is forced through corners and bends and the inlet.
16 foot diameter is twice what is permitted to go on roadways without EXTREME expenses like the wind turbine movers face just getting to a jobsite. Unless you're willing to pay those extreme fees, abnd the crane fees needed to erect those size monster pieces and parts .... $$$$$$$$$$$$$$$$$$$ .... then you need to make your duct in parts, and assemble on site by today's (largely unskilled) labor.
Make the parts shipable by truck and assembled on site with simple (cheap) flanged connections. The skin of your duct will be 1/4 inch to 3/8 thick thick. Split each ring into quarters (or thirds would be better.) Use the mating flanges (the round circumferential or axially-spaced flanges) spaced every 8 foot to stiffen the structure overall, and as erection-sized rings.
A smaller lift will mean less wind interference during erection/construction, and you can rent a smaller crane to move the parts - both in the fab yard onto the truck, and off the truck on-site. The longitudinal ribs will double as reinforcements against linear collapse and as "splits" The three (or four, if quarters) straight flanges going axially stiffen against collapse from wind and ice loads. A 16 foot diameter "non-pressure-containing) cylinder is "too big" to get much strength from its ring-like shape: If you make the walls thick enough to act "like a pipe" they will be waaaaay too expensive to make, lift or buy.
So your structural strength has to come from the axial and longitudinally-spaced stiffeners on the tin-walled tube.
You will need towers (bents) every three (maybe four) rings to hold up the complete assembly.
Structural loads on the 16 foot (5+ meter) diameter duct will include:
- Self-weight of the cylinder pieces - as they are fabricated, as they are shipped, as they are erected, and in-place (gravity) loads will distort and warp each section.
-External wind loads on each piece after erection.
-Warping from settlement of the assembly.
-Seismic?
Static, external loads: snow and ice loads?
-Vibration and internal loads as the weight of the dust is forced through corners and bends and the inlet.
16 foot diameter is twice what is permitted to go on roadways without EXTREME expenses like the wind turbine movers face just getting to a jobsite. Unless you're willing to pay those extreme fees, abnd the crane fees needed to erect those size monster pieces and parts .... $$$$$$$$$$$$$$$$$$$ .... then you need to make your duct in parts, and assemble on site by today's (largely unskilled) labor.
Make the parts shipable by truck and assembled on site with simple (cheap) flanged connections. The skin of your duct will be 1/4 inch to 3/8 thick thick. Split each ring into quarters (or thirds would be better.) Use the mating flanges (the round circumferential or axially-spaced flanges) spaced every 8 foot to stiffen the structure overall, and as erection-sized rings.
A smaller lift will mean less wind interference during erection/construction, and you can rent a smaller crane to move the parts - both in the fab yard onto the truck, and off the truck on-site. The longitudinal ribs will double as reinforcements against linear collapse and as "splits" The three (or four, if quarters) straight flanges going axially stiffen against collapse from wind and ice loads. A 16 foot diameter "non-pressure-containing) cylinder is "too big" to get much strength from its ring-like shape: If you make the walls thick enough to act "like a pipe" they will be waaaaay too expensive to make, lift or buy.
So your structural strength has to come from the axial and longitudinally-spaced stiffeners on the tin-walled tube.
You will need towers (bents) every three (maybe four) rings to hold up the complete assembly.
JedClampett
Structural
Check this thread out:
thread507-333983
It seems like I've never seen a question on hot gas ducts and thne there's two in a couple of weeks.
thread507-333983
It seems like I've never seen a question on hot gas ducts and thne there's two in a couple of weeks.
MiketheEngineer
Structural
I think you might be in over your head. Consider bringing in a pro??
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